Since the inception of the data storage disks, the industry has pushed towards higher and higher data storage densities by increasing the number of tracks per inch on the data storage disks. The tracks are concentrically formed on the disk with each track having a corresponding identification field that identifies the individual track. Track identification fields are used for positioning of a recording head which is moved essentially in the radial direction of the disk as the disk is rotated. Each time the head is made to face a track by the combination of disk rotation and head movement, the track identification field of the track is read by the head and the position of the head is determined by a series of calculations performed on the read data. In this way the head can be positioned over a desired data track for performance of a read or write operation on the data track.
The increase in the number of tracks, however, has resulted in a corresponding increase in the length of the track identification field that in turn has introduced an added delay in the processing of the read data for determination of the position of the head. The added delay may result in the passage of head across three or more data tracks (while the head is moved across the disk) before the determination is made, thus resulting in identification read errors and misconception of head positioning.
Currently, magneto-resistive heads are the preferred heads used in the industry. Such magneto-resistive heads, however, are also susceptible to traditional noise phenomena well known in the art which may adversely interfere with the reading of the track identification fields by the head. These noise phenomena, such as baseline popping (BLP), are generally manifestations of kinks and loops that are present in the media field range of the magneto-resistive transfer curve and which give rise to observed head instabilities. The adverse effects of head instability become even more pronounced in face of the foregoing added delay in the longer processing time of the read data for determination of the position of the head. The various conventional techniques that can be used to deal with head instability cover a broad spectrum of solutions from screening at the head level to adjusting the channel response. These techniques, however, are relatively complicated and expensive to perform.
Accordingly, what is needed is a less expensive and reliable technique that addresses both the problems of the longer processing time of the read track identification field and the head instabilities during the read.